Mechanical control for submerged hydrofoil systems



Feb. 23, 1965 J. K. ROPER 3,170,432

MECHANICAL CONTROL FOR SUBMERGED HYDROFOIL SYSTEMS Filed April 14, 1964 I 3 Sheets-Sheet l WATER FLOW BOUNDARY 7 h I, M- I I 26 ;6 266 :4? 252, 4 TI 27; i I I0 Li '15,, Cl I I I l II. I 27a 27 II] 5 I I 5 2 5; "n...

I I I 1 i 23 I :5 i I II r 1 5:: p": H M 24. 22 5L l8 /6 f5 INVENTOR.

Fl I JOHN A. DOPE/2 ATTODNE S.

Feb. 23, 1965 J. K. ROPER 3,170,432

MECHANICAL CONTROL FOR SUBMERGED HYDROFOIL SYSTEMS Filed April 14, 1964 3 Sheets-Sheet 2 I NVENTOR. JOHN K QOPED ATTORNE S.

Feb. 23, 1965 J. K. ROPER 3,170,432

MECHANICAL CONTROL FOR SUBMERGED HYDROFOIL SYSTEMS Filed April 14, 1964 5 Sheets-Sheet 5 I8 INVENTOR JOHN K. QOPEQ FIG. 5

ATTORNE 5.

;,in'-that priorpatentga control-fla 5 I I I drofoil is' mechanicallyflinked to a fve rticaltr-ailing'; ledge 'fiapFo the vertieal' strut Which supports submergedv e n -.3,170 43z' .1.;- MECHANICAL CONTROL FOR SUBMERGED a HYDROFOIL SYSTEMS I John; K. Roper, Stony Brook, N.Y., assignor to Atlantic .r Hydrofoils, Inc., Stony Brook, N.Y., a corporation of New .York

' Filed Apr. 14, 1964, Ser. No; 359,563

10 Claims. (Cl. 114--'66.5)

The-presentinvention'relates to an au'tomati c, passive, mechanical control system for stabilizing the motions of "ice,

actuates" the vertical flap so thatits deflection causes a deflection'of the fiapof the submerged foil which in turn increases the hydrodynamic lift force on the submerged hydrofoil'so as to'raisethe hullover the oncoming wave flank. The size of the submerged hydrofoil control flap,- the size of the vertical depth control flap on the vertical 1 support strut and the required mechanicallinkages bemarine craft which are supported by submerged hydrofoil systems and which are subject to operation under either calm water orwave conditions.

In'the operation of hydrofoil marine craft with uncontrolled submerged hydrofoil support systems, it is known that the craft requires some form of height stabilization control when-operating in either smooth Water or waves. In smooth water, uncontrolled submerged hydrofoil systems may-develop continuously oscillating, heaving and pitching motions or so-called divergent pitching or heaving motions which may cause the hull of the hydrofoil craft to crash' against the water surface. When uncontrolled submerged hydrofoil systems are run in a seaway, thewave disturbing forces can result in extremely uncomfortable heaving and pitching 'motions of: the craft and/or cause the bow of the hull to crash onto oncoming wave flanks. All the'above described events'can seriously hamperlor prevent successful operation of the In the past, many attempts were made to ;control the hydrodynamic forces on thesubmerged hydrofoil'by the. use of combinedelectroriic and-mechanical control systerns. 'These' control systems usually sense the-disturbance -of the craft byfcontinu'ously monitoring (usually electrically) the accelerations ;or motions of the cfaft and then,

by mechanical means,provide for'efifectiveangle of attack,

tween these flaps are arranged and proportioned to provide any desired sensitivity and response characteristics to Wave disturbances asto'assure a minimum total craft response to the hydrodynamic forces developed by opera-' tion in waves. g

The present invention utilizes the general mode of operation of said prior invention but, as one feature, pro-' vides for aventilated vertical flap which may be positioned on 'the streamlinedvertical support strut at any point other than that where both sides' of thisiflap are in streamlined alignment with the corresponding sides of said vertical support strut (where the profile ofthe flap and theprofile of the-strut are continuous), This provision for air ventilation of one surface 'of said flap permits the marine craft to operate without the heaving and rolling v which-may arise in craft havingfa vertical flap in symmetrical, stre'ar'nlinedprofile alignment with the vertical, strut. In such craft,rwhen the verticalflap is :pivoted,-the

I water flow across the negative pressure surface of the flap changes on thes ubmerged foils "to 'vary the hydrodynamic y t disturbing-forces on the hydrofoil in order to overcome the "w'ave'f disturbances. I These electronic-mechanical auto-pilot systemsa're complex [i111 design, require conponents becomes defective. Savits'ky'Patent' No. 3,092,062 ,.-dated June4,. 196 3, discloses a passive; 'm echanica'l automatically operating 1 simple hydrofoil control sy'ste m which possesses all the a advantages iof 'a subinergied hydrofoilfsysteni withoutthe I complexity, expense, and involved "maintenance {required I of electroni'crnechanical auto-pilot systems i hydrofoilito the hull iofrthe craft. 1 smooth water-cp eration of a marine craft using this fprio'r system, as a the hydrofoil boat tends to: fall towards 'thefwater surface, the 'vertical flap'ion the vertical support v st'rutl is so jarranged as toJbe-deflectdbythe hydrodynaniic'force de-i ffi "veloped bythe increased eifeetiveimm'ersion den er-flaps Through a: .suitable linkage-"system the deflection off the V vertical flap causes a deflectioirbf the con troliflap on the a 'subinergedhydrofoilg thus increasing the" hydrodynamic lift on the hydrofoil'and causing the hydr'ofoil craft "to rise until anjequilibriumaltitud'e is attained-"Atfsbrne pre-selected operating' heightf of the boat, t he;vertica1 flap is designed to be clear of the-water and-the hei'ght stabili} q zation is achieved'by the natural hydrodynamiephe nomena whereinthe submerged hydrofoil lq'ses hydrogains lift its submergen'cefis increased,

dyriainic lift as it approaches are; free wateriisurface I n -the use of thisprior s stenr on marine c'raftoperat ingyin'waves,' the"rising water surface of the 'wave profile tinuous maintenance, are costly,and could eauseahydro- 1 foil boat to be inoperable'if only one of its manycornmay erratically break away from this surface, particularly at higher boat speeds,'and thereby introduce air to said surface at a diiferent pressure than waterflow creates on the surface. The orientation of said-flap, and therefore of the submerged hydrofoil control-flap,-"will then change due to the change in differential pressure between opposite sides of the flap.

- In hydrofoil craft generally having two vertical struts and flaps with accompanyingmsubmerged'control flaps, this breakaway action may occur at onlyone vertical 'fiap due to small'constructional variations of the vertical struts and flaps, or dueto different strutsand flaps being exposed to different-wave motions. The breakaway act onat one vertical flapgand the resultantr'eorientation 4 of the submergedjhydrofoil control flap, will'therefore cause the craft .to roll; Breakaway action at both vertical flaps w1ll 'cause a pitching of 'thecraft-due to reorienrtatioii of bothlsubmerged control flaps. This'breakaway l ,actronoccurs randomly and is "extremely difiicultto pre-- vent-by design modifications. 1

7 provides, at all'tirn'es. when said verti cal flap is submerged,

. for an air cushion or'pock'et adjacent the surface of the vertical. flapiwhere breakaway. n'iightYbefekpected to occur; This. lair pocketfis' ,aiconstant, rather than erratic} parameter p and. is easily designed into the-me'cl' ani'cal hy-l drofoil controt system."'

' {Xnotherffeature offthe ip resent inventioniis the zpro I vision of two vertical and oppositely pivoting'fiaps to b'e' 'positionedonrthe verticalsupport fstrut'f The use of mad ciaft', ;the bending moment will tend toturn the craft and mustbe compensated for. The use of twolverticalflaps,

orientated on each vertical strut to pivot toopposite sides;

of said strut, respectively, alleviates both; of these} problems by'vbalancingfftwoibendiiig moments. againstjeach other t j each said strut. Additionally, the-..use of the "t wo' sa1d flaps :provides for 'ari i airxcushion' adjacent the Patented Feb. 23, 1965 The, ventilated vertical flap of the present invention 7 causes inner surface of each vertical flap,, and the breakaway? problem is avoided. t

v A further feature of thepresent invention is to providea'hydrofoil craft having vertical flaps of the forms described above, which may achieve self-compensating;

cruise equilibrium and maintain a relatively constant'level; of-"the craft above thenwater at a plurality rofclistinctly' difierent cruise speeds. Present hydrofoil craft, with'a l self-compensating submerged, control system such as de--- scribed in said prior patent, achieve such equilibriurnonly' within a'few, percentage points of one designed cruise: speed at which point the vertical flaps are completely out of the water. ;Varying;the speed of the boat over a. wider range changes the level of the boat above the Wa ter sufficiently to render its self-compensating control in-- effective at higher levels or to drop the boattowards the water so that it is-influenced by waves striking the boat r hull. a a

According to this further feature of the invention; the vertical flaps on the vertical [control struts are divided into a plurality'of distinct sections, each section providing self-compensating control of .the hydrodynamic lift. of the boat at a different cruise speed and maintaining thecraft at a relatively constant level over the water for each cruise speed: 7 V a v a I An additionalufeature of the present invention is the provision of. submerged-hydrofoil control means which are notsubject to the fiow'brealgaway problem discussed above in-relationto the'vertical flaps positioned on said vertical strut. v .7 A further-feature of the ,present invention is the provision of; vertical flap meansrpositioned on said vertical lift coefiicient to. be developed by the submerged hydrofcill and a large hydrodynamic .lift force is developed so'that the boat tends to lift itself out of'the water; As the speed of the craft is increased,'two conditions are de-r veloped. First; that the; required lift coeflicient to sup port the craft isdecreased and, secondly, theicraftfwill start to rise so that the' hull is lifted out of the Water; As the craft rises, the vertical fiapl l rises, immersion is reduced and its hydrodynamics load is reduced. "The-increased load on the submerged flap to causesits own deflection to be reduced and'iri turn, through the linkage system 17; causes the verticalflap 14 to increase its flap V angle until an equilibrium moment condition islachieved between the vertical flap and horizontal flap loads. This I ventedby a physical upperstop 18.;

a process continues; i.e., as the craft goes faster-{the hydrofoil flap 16 loads are increased, thecraft rises, reducing the effectiveness of the vertical 'fia'p 14 until thecraft 1 reaches an equilibrium cruise-height at which the vertical ha is completely outof the waterand the hydrofoil flap 1s no longer deflected, its further 'rnovement being pref .Further; increases inlcraft'heigh -raret thencontrolled by the hydrodynamic phenomena :which causes a reduo.

tioninhydrofoillift as the'subrnergeddihedral hydrostrut;whichjwill soften the response of-the submergedhydrofoil controls to larger wavesrand which will tend togdisregard small Waves of, insuflicient height to strike: the hull of the boat when it is at cruising speed.

v Othrffeatures and qthe' attendant advantages of ;the present invention will ,be readily appreciated by reference i to the following-description, when considered in connection with the accompanying drawings wherein? FIGURE 1' is a side view ofan e bodirnent ofthe present invention; illustrating a, hydrofoil system; which includes a ventilated flap. positioned on a. support strut vertically mounted tota' hydrofoil marinecraft;

I FIGURE '2 is-la sectionali view on line 2.1-2

support strut suitable fo'r' vertical Zmounting on: .a hydroge foill imarinencrafty 1;

JFIGURE URE 3;;and r.

FIGURE ;5 i's-aside viewjofa further jmbodirnenfiof the presentinvention5, illusttating 'a'flhydrof oil control sys- -t e'n1' 'whichinclud'es ai veritilate'd flap positionedFaS *in FIGURE 1, which flap is additionally .des'ignedi-f0r .;pro{ -viding self-compensating hydrodynamic lifit operation at a'vai iety of cruise speeds."

Re ferrir ig nov to thevdraw ngs svherein 1k reference characters designates;.corresponding structure throughout. .7: h rseveral viewsr there is shown in. F IG URE ;1 meirged hydrofoilrlttl attached to a vertical suppo 11 which is'inturn attached at its'top portion to the he rear-10f s merged'hydrofoilflt) at it'strailing'edg'e is' horiz'ontal 'con trol flap 1d, and a'mechanical linkage generally indicated as 17 connectsvertical flap 13% and horizontal 'flap ittvf- 3 j Vertical flapl t is shown in FIGURE l tobepa rtiahy V yirn'm'er'sed inwatehso thatits operation may b'e better' t .understood' 'IThis-imrnersion representsflow speed operain FIGflgi' FIGURE 318.3 side view ;of another embodilment "of the-present invention,illustrating. a hydrofoil control" sys-i r tem which includes twoventilatedfiaps positioned lona- 4 is anse'ctiona view on linegft a 11, adjacent side; 13st said strutiisvertrcal"flapl l l, which ,pivotsf-about strut edge 15. ,Pivotally attachedgto'subwateralong said side surface. At certain highenajboat' speeds, however, said tangentiallfiow-iof 'watei i'may' erratically intermittently-break frorn said'fiap stil face, and introduce airbtween the water flow aud said 1 surface. .fFheprfessur onjsaidjsurface then changestfrorn negative to "positive due to the an introduction) and r-ientation of the vertical flap'from I V "tion-of'theboa't, and thefhydrodynarnie. load-onfiap l t V p ful-l down defiection of submerged ehyfdrofoil lls-p16 Thisfull down deflection offia'p lbauses a large L le eychansesi 1 along -;in{ contact :withL-said surface,

maihsbi ti e e e e 1 10 s ru .rearwardly alon" foil approaches 'the freewatensurface. If, for some reason, the craft is vcaused'ito move towards; the free 7 water surface, the vertical fiap 14 isthenactuated causing a deflection of the hydrofoil flap'16,"which in turn causes the; hydrodynamic lift'foree to be increased and dition. g g, ThlS operation as so far. described} the same asset hence causes the craft to rise again to anequilibrium conforth in said prior patent In saidsprior system, however;v

the vertical flapis in the shapefof a streamlined air foil, and is-positioned at the trailing fildgfi 'Of'jthfi5trafl1iln6d v vertical strut such that both of :its's ides, respectively, on- 1 stltute streamlined c ontinuation s; of: the twoside surfaces of said strutm As said flap;encountcrs water flow and P YQl 'o e s d ris; di ctly c i o' d t pfi t v fo c f, waterhow and the-otherg sidezis exposedtto a suction ornegative pressure,Ecreated hyL-theitangentialowof what it 'is designs to be when. water. tangentially :fiows acts throughfthej mechanicalglinlgageito change; the orien a of hei hiurggd hydro il fi 's,,; nd th beat/is" 1 e :7, I away atstru clge'gll ma stablestreamras shown n a h Q n i si lt l stt r p s to. th

own, 1nFIGURE 1, astth g sid zofjsaid 'strutg' or it-L to ex ten d rear reorientation 5 strut. In either case flap 14 is asymmetrically mounted with fore and aft axis 1919 of vertical strut 11 and one side of said flap will always be ventilated with a layer of air adjacent thereto so as not to be exposed to a control disturbing, intermittent tangential flow of water at certain boat speeds.

The ventilated flap- 14 described above, having less pressure differential between the two sides of the flap than in said prior system, does not exert the degree of bending moment on strut 11 thatv the streamline-d, symmetrically mounted vertical fiap of the prior system provides. The structural reinforcement required for the vertical support strut is therefore substantially less. .In addition, the flow characteristics around the strut and ventilated flap are of course changed from the prior system, and the ventilated flap orientation is found to provide less hydrodynamic drag at the support strut.

Ventilated flap 14 may be in the generally rectangular form of the flaps shown in FIGURE 3, but a downwardly tapered shape as shown for flap 14 in FIGURE 1 has been found to have distinct advantages. When the hydrofoil craft is at cruise speed, with flap 14 out of the water, short waves of insuflicient height to strike the hull of the boat will only react with the lower, small area portion of flap 14; the response of the hydrofoil craft will be relatively slight, as it should be for waves which will not affect control of the hydrofoil. Higher waves will react with the entire area of flap 14, and the hydrofoil craft will essentially contour and lift over these waves. Tapered flap 14 is again of value, since the lower, small area portion thereof will tend to ignore the small chop found on top of many waves. The gradually increasing sensitivity of flap 14, due to its tapered configuration (which may be linear or curvilinear), essentially softens the response of the hydrofoil craft to all waves by providing for said waves to react with flap 14 in a smoothly increasing fashion. A further means of varying said respouse, if desired, is to twist flap 14 into various configurations.

Flap 16 is shown in FIGURE 1 pivotally mounted .to the trailing edge of hydrofoil 10. In hydrofoil craft designed for very high speeds, however, such a mounting may cause water flow along surface 22-of said bydrofoil to breakaway from surface 16a of flap 16 when said fiap is pivoted'in a downward direction. Cavitation plate 23 mounted below flap 14 onstrut 11, will prevent air being introduced to surface 16a, but water vapor will form between surface 16a and the adjacent water flow. This breakaway at flap 16 affects the flow characteristics over the entire hydrofoil 10, and renders said hydrofoil much less effective as a lifting agent. An arrangement to obviate this breakaway problem is, to: do away with flap 7 16 on the trailing edge of hydrofoil 10, and in fact to utilize the entire hydrofoil as a flap by pivotally mounting said hydrofoil at 24 (shown in phantom at the hydrodynamic center of pressure of hydrofoil to vertical strut 11-. Hydrofoilllhdue to'its large surface, then only needs to be pivoted slightly to provide the same amount of lift as would be provided by a fiap 16 pivoting to a larger. extent, and therefore will not encounter the flow breakaway which might occur over said fiap 16.

. Linkage17 shown in FIGURE 1 consists of pushrod 25, triangular linkage 26 and push rod 27. Vertical push rod 25 is pivotally mounted at one end 25 1 to flap 16, and is pivotally mounted at its other end 25b to vertex 26a of triangular linkage 26. Vertex 26b'of said linkage is pivotally aflixed to vertical strut11, and vertex 26c.

is pivotallyconnected to end 27a of push rod 27. The other end 27b of push rod 27 isipivotally connected to flap 14. When water fio w intersects vertical flap 14, causing it to pivot, triangular linkage 2.6 in turn pivots about up and down motion of push rod 25 and pivoting motion deflection rate by merely changing the positions of pivo points 26a or 260 relative to fulcrum 26b.

, vertex 26b and translates said flap pivoting motion into o of m 1s. The deflection rate of one said flap may be adjusted to any desired proportion of the other flaps Push rod 27 may be replaced by a stilt spring such as shown at 28 in FIGURE 5, with said spring acting as a rigid normal linkage at most speeds but compressing when flap 14 is exposed to high water flow pressures associated with very high boat speeds. At such high speeds, when flap 14 is exposed to water flow, the large forces on said flap causing it to severely pivot would normally be transferred to pivotal hydrofoil 10 or flap 16 to provide an undesirably large lifting force to the boat. Spring 28, by compressing when subjected to the large forces associated with high boat, speeds, absorbs the pivoting motion of flap 14 and thereby prevents said large lifting force to be applied to the boat.

Referring now toFIGURE 3, an embodiment of the present invention is shown wherein two vertical flaps 14 are mounted on strut 11 to respectively pivot about edges 15 and 15a thereof in opposite directions. In certain forms of hydrofoil craft having one vertical support strut mounted on the forward position 0 fthe boat hull and two on the rearward portion, a single vertical control flap mounted on said forward strut and pivoting only to one side thereof acts as a' second, undesirable rudder and tends to turn the hydrofoil craft. In these forms of hydrofoil craft, as well as other forms having two vertical support struts mounted on the forward portion of the boat hull and only a rudder strut mounted on the rearward portion, the forces on the single vertical control flap mounted on each said strut creates large bending moments on each strut which must be structurally compensated for to avoid buckling of the strut. Oppositely pivoting flaps 14, extending rearwardly on opposite sides of fore and aft axis 1919 of strut 11, create opposite.

bending moments on strut 11 which essentially balance each other out when sides 14a are exposed to water flow. No turning moment is therefore exerted on the hydrofoil craft, and strut 11 and its mounting to the boat hull need not be structurally reinforced. Flaps 14 may in fact be.

crum 30a to pr-otrudingsection 31 which is integrally affixed to strut '11. Vertex 30b of said triangular linkage is pivotally connected to push rod 32iwhieh is in turn pivotally connected to submerged flap 16. Horizontal r0d'33 is integrally aflixed to vertex 30c of triangular linkage 30, and the 'ends of said rod are pivotally connected .to the ends of push rods 34 and 35, repectively. The

opposite ends of push rods 34 and 35 are in turn pivotally connected to horizontal projections 36 and 37 of flaps'll i, v

respectively. When flaps 14 are exposed to water flow, they pivot towards the fore and aft axis 1919 of strut 11, and linkage 29 transmits said pivoting motion to flap 16. Push rods 34 and 35 may be replaced by stiff springs which are only compressible under high pressure, flaps 14 may be tapered, and submerged flap 16 may be eliminated'with entire hydrofoil lflpivotally connected to strut 11, all as discussed above in reference to FIGURE 1'.

Referring to FIGURE 5, flap is pivotally connected to strut 11 exactly as in FIGURE 1, and is linked by linkage17 to flap 16 as shown in FIGURE 1, with the exception of stiff spring 28 described above. I Flap 140 differs from flap 14 in FIGURE 1, however, in that it is configured to provide for the hydrofoil boat to cruise at two distinctly different cruise speeds with self-compensating control. rectangular or triangular configurations as shown .in

FIGURES 11 and 2, the hydrofoil craft'is designedto In hydrofoil craft with flaps 14 having 6 v cruise at a given speed at which flaps 14 are completely above the surface of the; water. This designed cruise speed of the boat may bevaried upwardly or downwardly within a range of several percent bymanually pivoting a horizontal submerged trimmer flap mounted to a vertical'strut at the rear of the boat. This trimming flap is not part of the invention and is not shown in the drawd ings. 'Pivoting the trimmer flap causes the boat to nose' upwardly or downwardly, depending on the direction of said pivoti g, and the boat will cruise at the new speed with flaps 14.,stil1 out of the. water. Certain hydrofoil craft, however, are requiredto cruise at speeds varying 1 level at approximately sixty knots cruising speed. The

difference betweenrthese two levels is. small compared to the height of the strut 11. Also, since section 39 is small in area, compared to section 38, it has small effect on self-compensating control of the craft at twenty knots. Two factors influence the difference in operating levels of the boat at different cruise speeds; nam y, the outward angular offset of section 39 to section 38, and the horizontal length. dimensions of section 39. As either or both of these factors increase, said difference in operatinglevels may, of course, be decreased, since section 39 becomes a more effective flap section. In FIGURES, for example, section 39 may be offset from section 38 to take a different anglethan section '38 with fore: and aft axis 19p19 of strut 11., The configuration of help 14 in FIGURE 5 may in' fact have a plurality of distinct;

sections for a'plurality" of distinct cruise speeds, and each section may take a variety of shapes depending upon the responsecharacteristic desired.

While the invention has been disclosed herein in connection with particular embodiments and specific structural details, it is clear that numerous-changes and modificationscould be made by those skilled in the art without departing from. thc'spirit and scope of the invention.

What is claimed is:

' causing it IOfpiVOL'tO apply'tosaid vertical flaps forces said hydrofoil plane includes a part fixed to the vertical strut, said horizontal flapbeing pivoted to said-fixed part and forming a trailing edge of saidplane.

3. The combination according to claim 1, wherein said mechanical linkage means includes a spring deformable only under high pressure and through which said force is applied. 7

4. The combination according to claim 1, wherein said vertical hydrofoil strut member has a substantiallyplanar. trailing surface and said substantially vertical flap is.

pivotallyniounted thereon to extend rearwardly from one side of said trailing surface.

5. The combination according to claim '1, wherein said rearwardly extending, substantially vertical pivotal flap. has a trailing edge which converges toward said vertical axis as said edge extends downwardly. j

- 6. In combinationwith a water borne vessel, a passive self-comepnsating hydrofoil control system comprising a substantially vertical streamlined hydrofoil strutconnected at its upper end to the hull of the vessel, said strut having a central fore-to-at't axis; a hydrofoil plane connected to the lower end of said strut and operable to maintain a hydrodynamic lift of the vessel .to, a minimum submergence of the hydrofoil plane below the free water surface at cruise speed of the vessel, said hydrofoil plane being formed at least in part by a horizontal flap pivotable relative to the strut; first andsecond vertical flaps; means securing said vertical flaps to the vertical strut for. pivotal thereof is exposed to water flow, said vertical flaps terminating at their lower ends at a height above said hydrofoil plane which is greater than said minimum submergence;

and mechanical linkage means connecting said vertical flaps to said horizontal fiap and operable, on application of unbalanced external forces to the horizontal flap 7 actingpto swing them in opposite directions toward posi- 1. In combination with a'water'borne vessel, a passive self-compensating; hydrofoil control system: comprising a substantially verticalstreamlined hydrofoil strut connected at its upper end to the-hull of the vessel, said strut having a central fore-to-aft axis; a hydrofoil plane connected to the lower end of Saidstrut and operable'to I maintain a hydrodynamic lift of the vessel to a minimum l submergence of the hydrofoil plane'below the free water surfaceat cruise speed of the vessel, said' 'hydrofoil plane being formed at least in part by a horizontalfiap pivot- I able relative tothe strut; a vertical flap; means securing the vertical flap to'said strut for pivotal movements about a vertical axi's offset toone side of said fore-to-aftaxisf and from'whi'ch said vertical flap extends. rearwardly, the

profileof saidvertical flap forming'a distinct discontinuity with the profile of said vertical strut, whereby one "side. of saidvertical flap partly defines an air pocket when the? opposite side of said'verticalflap isexposedto the water said minimum submergence; and mechanical linkage means interconnecting both of said pivotal fiaps: -'aridt operable, on application of unbalanced external forces to one flap causing it-to pivot, to applytothe other flap a j force acting to movesaid other flap toward aposition' for equalizingthe forcesjapplied to both flaps.

: fiowpsaid vertical fiap rterminatin g at its lower end at a heightabovea'said hydrofoil planejwhich is .greaterv than" tions such thatthe-forces on said verticalflaps equalize the forceson the horizontal flap.

7. The combination according to claim 6 wherein said mechanical linkage means comprises a first push'rod, an intermediate triangular "linkage, and second and third push rods, one end of said first push rod being pivotally connected to said horizontal flap, the other end of said first push rod being pivotally, connected to afirst vertex of said triangular linkage, said traingular linkage being pivotally connected to .said vertical strut member at a second vertex,- one end of each of'said' second and third push rods beingpivotally connected .to ,said triangular iinkageat a'third vertex, and the other ends of said second and third push rods being pivotally connected, respectively, to said vertical strut member flaps. i

8. In combination with a water borne'vessel, a'passi ve self-compensating hydrofoil controlsystenrcomprising a substantially vertical streamlined. hydrofoil strut connected at its upper end to the hull of the vesse1,-isaid strut having a'central fore-to-aft axis; a hydrofoil'plane connected to'the lower end of said strut and operable to' v maintain a hydrodynamic lift offthe vessel to a plurality V ofminimum 'subrnergences ofthe-hydrofoihplane below the free water surface at a plurality of distinct cruise speeds of thegvessel, said hydrofoil plane being formed at least in art by a horizontal pivotable .relative to the strut; a vertical flap which includesaplurality of distinct sections, eachsaid section substantially terminating at its lowerlend iat' a heightab ove said hydrofoil plane'which is greater than ajminimum,subrnergence at a cruisespeedg means fsecuring 'the;vertical flap to said strut for pivotal;

movements about a vertical axisoffsetsto'onefside of said fore-to-aft axis and from which said vertical flap extends rearwardly, the profile of said vertical strut flap forming a distinct discontinuity with the profile of said vertical strut, whereby one side of said vertical flap partly defines an air pocket when the opposite side of said vertical flap is exposed to the water flow; and mechanical linkage means interconnecting both of said pivotal flaps and operable, on application of the unbalanced external forces to one flap causing it to pivot, to apply to the other flap a force acting to move said other flap toward a position for equalizing the forces applied to both flaps.

9. The combination according to claim 8, in which said vertical flap includes upper and lower sectionsforming a gap between them, said lower section being of smaller area than the upper section.

10. In combination with a water borne vessel, a passive self-compensating hydrofoil control system comprising a substantially vertical streamline hydrofoil strut connected at its upper end to the hull of the vessel, said strut having a central fore-to-aft axis; a hydrofoil plane connected to the lower end of said strut and operable to maintain a hydrodynamic lift of the vessel to a minimum submergence of the hydrofoil plane below the free water surface at cruise speed of the vessel, said hydrofoil plane being formed at least in part by a horizontal flap pivotable relative to the strut; hinged means on said vertical strut for continuously maintaining an air pocket on one side of said means, said hinged means including a vertical flap pivot-able on a vertical axis and extending rearwardly therefrom, said vertical flap having a profile forming a distinct discontinuity with the profile of said streamlined vertical strut, whereby one side of said vertical flap partly defines an air pocket when the opposite side of said vertic-al flap is exposed to the water flow, said vertical flap terminating at its lower end at a height above said hydrofoil plane which is greater than said minimum submergence; and mechanical linkage means interconnecting both of said pivotal flaps and operable, on application of unbalanced external forces to one flap causing it to pivot, to apply to the other flap a force acting to move said other flap toward a position for equalizing the forces applied to both flaps.

No references cited.

FERGUS MIDDLETON, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,170,432 February 23, 1965 John K. Roper It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 4, line 48, for "therbey" read thereby line 68, for "joints" read joins column 6, line 21, for "o fthe" read of the column 8, line 18, for "selfcomepnsating" read self-compensating line 52, for "traingular" read triangular line 69, after "horizontal" insert flap column 9, line 8, strike out "the".

Signed and sealed this 27th day of July 1965.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

1. IN COMBINATION WITH A WATER BORNE VESSEL, A PASSIVE SELF-COMPENSATING HYDROFOIL CONTROL SYSTEM COMPRISING A SUBSTANTIALLY VERTICAL STREAMLINED HYDROFOIL STRUT CONNECTED AT ITS UPPER END TO THE HULL OF THE VESSEL, SAID STRUT HAVING A CENTRAL FORCE-TO-AFT AXIS; A HYDROFOIL PLANE CONNECTED TO THE LOWER END OF SAID STRUT AND OPERABLE TO MAINTAIN A HYDRODYNAMIC LIFT OF THE VESSEL TO A MINIMUM SUBMERGENCE OF THE HYDROFOIL PLANE BELOW THE FREE WATER SURFACE AT CRUISE SPEED OF THE VESSEL, SAID HYDROFOIL PLANE BEING FORMED AT LEAST IN PART BY A HORIZONTAL PLANE ABLE RELATIVE TO THE STURT; A VERTICAL FLAP; MEANS SECURING THE VERTICAL FLAP TO SAID STRUT FOR PIVOTAL MOVEMENTS ABOUT A VERTICAL AXIS AFFSET TO ONE SIDE OF SAID FORE-TO-AFT AXIS AND FROM WHICH SAID VERTICAL FLAP EXTENDS REARWARDLY, THE PROFILE OF SAID FLAP FORMING A DISTINCT DISCONTINUITY WITH THE PROFILE OF SAID VERTICAL ATRUT, WHEREBY ONE SIDE OF SAID VERTICAL FLAP PARTLY DEFINES AN AIR POCKET WHEN THE OPPOSITE SIDE OF SAID VERTICAL FLAP IS EXPOSED TO THE WATER FLOW, SAID VERTICAL FLAP TERMINATING AT ITS LOWER END AT A HEIGHT ABOVE SAID HYDROFOIL PLANE WHICH IS GREATER THAN SAID MINIMUM SUBMERGENCE; AND MECHANICAL LINKAGE MEANS INTERCONNECTING BOTH OF SAID PIVOTAL FLAPS AND OPERABLE, ON APPLICATION OF UNBALANCED EXTERNAL FORCES TO ONE FLAP CAUSING IT TO PIVOT, TO APPLY TO THE OTHER FLAP A FORCE ACTING TO MOVE SAID OTHER FLAP TOWARD A POSITION FOR EQUALIZING THE FORCES APPLIED TO BOTH FLAPS. 